[Finishes #75528614] no concrete blocks for jigsaw

We originally conceived of concrete blocks (blocks that transition between toolbox and workspace instead of duplicating) as a way of making blocks/toolboxes less confusing for K1 students.  We used them in Jigsaw with the expectation that they were also going to be used elsewhere, however, we ultimately have not used them elsewhere.

This gets rid of concrete blocks from Jigsaw.  It then adds a trashcan to the Jigsaw levels that have toolboxes (otherwise if you drag in two blocks from the toolbox, you can no longer complete the puzzle).  It also makes the start blocks non-deletable.  They can actually still be deleted if you try hard because of https://www.pivotaltracker.com/story/show/75530594 but I think we can live with that for now.